SP is when your body is paralyzed. It prevents you to move in real life if you move in a dream.
WILD is basically trying to trick your body and make him think your mind is alseep, when it isn't. Then paralyze the body, and create dreams.
BUT, I had 3 SP's in my life, and it's pretty weird.......
The first one : I was struggling, trying to get back to sleep, early in the morning. It was the night I discovered how SP's was awesome but I didn't want one. After one hour, I was really angry. I couldn't think of anything else beside SP so I punched my bed really hard, changed side, and then the Sleep Paralysis occurred right after I moved violently(I wasn't sleep breathing, at all)

The second time : It was the next night, I wanted to try it again just because I liked the sensation. And guess what ? It worked. I got out of it after a few moments though, I wasn't really emotionally prepared. (I did sleep bread)

Then, I had about a couple of weeks when I didn't think about it at all. I was still struggling trying to get to sleep and everything but even if I didn't move for an hour, I didn't get sleep paralysis. I just didn't though about SP, and just continued my quest to falling asleep
The third time : It was last night. When I got to bed, I just quickly though about SP and how I will need to master it later when I will be good with MILD. I though about it for about 5 seconds, and then though about something else. About 5 minutes laster, I got sleep paralysis. I was thinking some song I like and the song just got really really loud and I was feeling that buzzing thing on my body, exactly like the first time I SP. I quickly got out of it because I knew I would just fail and get my heart pumping like hell, keeping me awake.

What IS Sleep Paralysis ? Trust me, it can't be a coincidence. I think this is very weird..
Also, when we think about it, do we really need to stay still ? The first time I had it, it was just after a super falcon punch on my mattress
I don't want to have it again for now, but it's picking my attention.

I really don't have experience with SP, I only had one and that lasted just a few sec. because I start to wonder if is this a SP or not, and then it just slipped away, although the dream I had then was FLD, and it was one of the most intriguing experiences... (of course nothing like LD, but still )...

And about all that, I liked the way I was conscious about real body and dream body at the same time... It's cool experience!

Pretty strange, your first SP... it's pretty much impossible to get into SP after you do a violent move. For me to reach SP, I have to stay like 10 minutes daydreaming. When I am about to lose consciousness I get the SP like a "pulling sensation". That brings my conscious back. But yeah, after some time with this sensation I get back to normal fully awake... . In fact I never actually finished such a SP feeling - if it was SP. (I only experienced SP like you described it in your 3rd experience).

Now we are all different so we all have different dreams and thus we all have different ways of achieving lucidity or SP or whatever. You should try that more times - see what happens if you stay absolutely motionless and focus just on the feeling. Simply feel it - don't do anything else.

I've been trying to do that myself but each time everything is so intense that I freak out of it... . Anyways, I think SP is SP. It can sometimes occur strangely but it's still SP and it's natural.

I fall asleep with SP. I'm to the point where I just tell my body to go into SP, and it does pretty quickly.
For me, it feels kinda tickly/tingly and then I just have no sense of feeling there at all. If my hands are in a ball, I can no longer feel my other fingers until I force myself out of SP. It also feels, for me, like I'm under a super heavy blanket.
The best time I ever got into SP before I fell asleep, my body was completely under SP except my eyes. It was really cool.
As you can tell, SP has never been a bad experience for me, just something that has dramatically reduced the time that I have to lay in bed each night, waiting to fall asleep.